如何返回如果輸入不等於;批處理文件

Question

我一直都在做一個批處理文件來執行程序

@echo off 
:top 
set /p choice=" My Choice = " 
if %choice%=="install program.alpha" goto alpha 
if %choice%=="install program.beta" goto beta 
:alpha 
start="Destination...." 
goto top 
:beta 
start="Destination...." 
goto top 

所以我的問題是。我不能創建一個條件，當用戶輸入錯誤的命令，所以它必須返回一個錯誤。比如用戶輸入的命令：

install program.gamma 

或

install program.alhfdzbd or something else that not matches the custom commands 

我能做些什麼???

Answer 1

如果用戶既不輸入install program.alpha也不輸入install program.beta，只要將輸入視爲無效。

@echo off 
:top 
set /p choice=" My Choice = " 
if "%choice%"=="install program.alpha" goto alpha 
if "%choice%"=="install program.beta" goto beta 

:: If you get here, the user has typed something wrong. 
echo Invalid selection. Exiting. 
exit /b 

:alpha 
set start="Destination...." 
goto top 
:beta 
set start="Destination...." 
goto top